This invention relates to a swash-plate type compressor, and more particularly, to an improvement of a bearing device disposed between the swash-plate and the piston.
A swash-plate type compressor here signifies a compressor wherein a swash-plate secured to a rotary drive shaft with a certain angle thereto is being engaged with a piston which is parallelly disposed to the rotary drive shaft, so that the latter is reciprocated owing to the rotation of the former. From such a structure the engaging portion of the swash-plate and the piston must be protected by a bearing device by all means. A technology of employing a shoe of substantially semi-spherical shape is disclosed in the specification of U.S. patent application numbered with Ser. No. 071,616 now abandoned filed by three coinventors out of the four coinventors of this invention. And an idea of employing semi-spherical shoe in a reciprocating engine or pumps of swash-plate type which is rather similar to the compressor is discribed in some literatures such as U.S. Pat. Nos. 2,672,095, 3,938,397, 3,939,717, 4,030,404, etc.
The semi-spherical shoe used as a bearing device functions as a transmitter of drive force from the swash-plate to the piston, while slidably contacting at its convex spherical surface with a concave spherical surface formed in the piston and also slidably contacting at its flat surface with a flat surface on the swash-plate. Employment of such a semi-spherical shoe as a bearing device contributes a great deal to miniaturization, weight lightening, and cost economizing of a compressor, it is true indeed. It turned out, however, from the later study by the co-inventors that this device is still not free from the problem of durability.
A compressor according to the disclosure U.S. Ser. No. 071,616, is mainly used in air conditioning of cars for compressing refrigerant gas therein, and usually driven by the engine for the car driving. The semi-sphere shoe in the compressor is lubricated by oil mist contained in the circulating refrigerant gas. The amount of the oil mist supplied to the required sliding places is liable to decrease, when the engine is in an idle driving state, through remarkable decrease of the rotation number of the compressor accompanied by decreasing of the circulated refrigerant amount. This shortage of the oil mist carried by the circulating refrigerant is liable to make the sliding places of the semi-sphere shoe, particularly the sliding surface with the swash-plate, frictional leading to wear and seizure of the flat-side surface of the shoe, which might some time invite shortening of compressor's life.